Balanced directional gyroscopic instrument



Sept. 23, 1941.

o. E, ESVAL ETAL BALANCED DIRECTIONAL GYROSCOPIC INSTRUMENT v 2 m s n t R g T 0 .r w w u m H H A. mE

Filed Oct. 18, 1939 Sept. 23, 1941. o. E. ESVAL ETAL 2 3 BALANCED DIRECTIONAL GYROSCOPIC INSTRUMENT Filed Oct. 18, 1939 4 Sheets-Sheet 3 lmllllml I B M l ys/R ATrbRNEY Sept. 23, 1941. o. E. ESVAL HAL BALANCED DIRECTIONAL GYROSGOPIC INSTRUMENT Filed Oct. I8, 1939 4 Sheets-Sheet 4 MOTOR GENERATOR Puma ,04 INVE NTORS puma E. Es v/ufi' Jbssm 55/ me BY KZoRNEY v Patented Sept. 23, 1941 UNITED STATES} PATENT oFncs BALANCED DIRECTIONAL GYROSCOPIC INSTBUMEN Orland E. Esval, Allendale, N. .L, and Joseph Frei tag, Jackson Heights, N. Y., assignors to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a

corporation of New York Application October 18, 1938, Serial No. 235,566

7 Claims.

of the gyroscopic element around its vertical axis of suspension, thereby causing errors in its indications.

The present invention overcomes this difliculty by providing two completely separate individual gyro rotors, each having its own driving means and so disposed with respect to the horizontal and vertical gimbal axes that there exists complete symmetry around all axes as far as the gyroscopes and their mountings are concerned. Our novel directional instrument has no vertical ring, but condenses the vertical ring into a substantially vertical shaft carrying a pair of closely spaced bearings for a horizontal member supporting the gyroscopic elements outwardly therefrom in cantilever fashion. If these gyroscopes are substantially identical, it is obvious that there will be very little difiiculty in obtaining an accurate balance of the sensitive element of the instrument around the horizontal axis, and as both gyroscopes increase their temperature together and simultaneously, no shift of the center of gravity should occur due to unequal expansion.

Another object of the invention is to provide a safety-factor in operating this instrument, as the device will still be fully operative and only sufier very small loss of accuracy if one of the two gyroscopes becomes inoperative and stops rotating.

This invention also provides means for automatically disconnecting the electrical supply to the inoperative gyroscope, the windings of which might otherwise be damaged by excessive heating, after the rotor has ceased to rotate. There also is provided a novel means to eliminate the error which would resultfrom the contraction of the gyroscope due to its slowly falling temperature after the supply is disconnected.

Referring now to the drawings,

, screws 23.

tion of our novel direction indicating instrument.

Fig. 2 shows a top view of the sensitive element itself.

Fig. 3 shows a partly sectionalized side elevation of the sensitive element of Fig. 2 along line A-A.

Fig. 4 shows the caging mechanism for the' gyroscopic element.

Fig.5 is a continuation of Fig. 4, showing the lever for actuating the caging device.

Fig. 6 is an enlarged cross-sectional view of one of the preferred forms of gyroscope used in this invention.

Fig. 7 is an enlarged cross-section of the shaft of the gyroscope.

Fig. 8 shows the device which holds the tem perature of the gyroscope substantially constant after it has stalled.

Fig. 9 is a general wiring diagram.

Fig. 10 illustrates the means of electrically and mechanically connecting the hair spring conductors.

Referring now to Fig. 1, a base structure Iis suitably secured to the vehicle or craft on which the instrument is carried. A cover 2 secured by screws 3 serves to enclose the instrument and at the same time affords, through a window l, a view of the dial 5 which swings aroimd a substantially vertical axis and has an indicator 6 connected to the casing 2. The dial 5 comprises ouly a sector of about to and is carried by a vertical shaft 1 which is pivoted a bracket, H which is fastened to the base structure I, while the lower bearing 9 is encased in a hub l2, which is journaled in the base structure I by means of two ball bearings l3 and M. A thrust bearing in the form of a steel ball I5 is employed to absorb the pressure of the weight of .the gyroscopic element and the shaft.

The vertical shaft 1 in its middle portion carries two ball bearings l6 and I], as shown in Fig. 3. These ball bearings serve as journals for two adjustable conical pivots l8 and I9 which are carried in a casting 20 which is so shaped as to form the end shells for the two gyroscopic housings 2| and 22. These housings are'secured to the shell casting 20 by means of As shown in Fig. ,2, the shell casting 20 has a central aperture 24 through which the vertical shaft I extends and which is shaped Fig. 1 shows a partly sectionalized side eleva-tfi in such a way as to allow a limited amount of freedom for the gyroscopic structure to tilt in a vertical plane. The two housings 2| and 22 are identical and contain identical gyroscopic rotors with their driving statrs,- shown more in detail in Figs. 6, '1 and 8. 1

An arm 25 extends perpendicular to the gyroscopic axis, as shown in Figs. 2 and 3 and carries a number of screw studs 25, 21 and 23 which serve the purpose of balancing the structure around both horizontal axes by means of nuts threaded onto the studs. Opposite to the arm 25 there is attached to the casting 20 a bracket 23 which carries three small helical springs 35 serving as current conductors to supply the two gyroscopes with alternating current of a suitable high frequency. The free ends of the helical springs 30 are affixed to electrical contacts 3| carried by a bracket 42, but insulated therefrom by Bakelite bushings 33, as shown in Fig. 10. The bracket 42 is integral with the vertical shaft 1 and forms a horizontal projection on it, as

. shown in Fig. 3. A Bakelite strip 34 is mounted opposite the contacts 3| in such a way that by tightening screw 35 it can be clamped against contacts 3|. The free ends of the springs 30 are inserted between the Bakelite strip and the contacts 3| and securely held in position as soon as screw 35 is tightened. This forms an easy means of quickly connecting the springs, at the same time affording the possibility of adjusting these springs so as to stay in their own helix plane without lateral distortion in case of=-tilt of'the gyroscopic structure. From the contacts 3|, wires lead to a similar group of helical springs 35, as shown in Figs. 1 and 3, grouped around the lower part of the vertical shaft 1. A suitable bracket, not shown but similar in construction to bracket 32, is employed to fasten the free ends of the springs 35. This bracket is mounted on gear 31, Fig. l. The bracket itself is mounted 'behind springs so that it is not visible. From there three wires lead through a. hole 38 in the gear 31 and are grouped with other wires into a flexible cable 39 to afford limited horizontal motion for the gear 31. A clamp 43 holds the other end of the cable 39, from where the wires finally lead to a terminal block 4| which serves the purpose of affording convenient means of connecting external supplies and other electrical accessories.

The arm 25 and the shelf 42, extending to either side of the vertical shaft 1, as shown in Fig. 3, also carry two armatures 43 and 44 composed of magnetic material. These armatures are normally located opposite two pick-off transformers 45 and 45, only one of which is visible in Fig. 1. The transformer 45 has three coils 41, 43 and 49,each one encircling one of the three legs of the pick-off transformer. The transformer 45 is identically constructed with coils 53, 5| and 52. Both of these transformers are mounted on the gear 31, which in turn is rigidly connected to the hub l2. In their normal position, the armatures 43 and 44 are symmetrically located with respect to the center legs 45 and 5|, respectively, of the two transformers. The center cells. .48 and 5| of both transformers are excited from one phase of a three-phase A. C. supply, while the outside coils 41-43 and 53-52, respectively, of each transformerare oppositely connected to each other, but each group of two coils is in series with the other group of two coils in such a way that a differential signal of considerable magnitude is developed as soon as the armatures 43 and 44 are angularly displaced pinion 51 to' the azimuth gear 31.

a small amount from their neutral position with respect to the transformers. The secondary coils 4149 and 55-52 are wound in such a way, that the sense of winding of coils on one transformer is opposed to the sense of winding on the other transformer. Thereby any errors due to induction in these coils caused by the stray fields of the gyroscope stators are completely compensated. Theinduction causes equal and opposite potentials to appear in the windings, and, as the windings are connected in series, the potentials neutralize each other. In a similar way, the two diametrically disposed transformers prevent mechanical imperfections, such as for instance, looseness of bearings 5 or 9, from causing tum errors in the motor driven part of the system, because such defects will affect both transformers in opposite sense.

The wiring diagram in Fig. 9 shows the coils 41, 45 and 43 of transformer 45, as well as the coils 50, 5| and 52 of transformer 45. The primary coils 45 and 5| are shown as connected inseries to the terminals 53 and 54 of the terminal block 4|. A phase shifting network consisting of resistor 55 and condenser 51 serves the purpose ofv adjusting the phase of the excitin current for coils 48 and 5|. The primary threephase current of a relatively high frequency, say 500 or 600 cycles per second, is produced by the motor generator 55 and from there led to the terminals 53, 54 and'55 of the terminal block 4|, as well as to an amplifier 59. The differential signal output of coils 41, '49 and 55, 52 is led to terminals 53 and 55 of the terminal block, and from there enters into the amplifier 59, where it is amplified by well known methods to such an extent as to enable suitable control of a motor 5| which is electrically connected to terminals 52, 53 and 54. The three-phase supply as coming from terminals 53, 54 and 55 also passes .through the three horizontal liair springs as,

from there through the three vertical hair springs 30, through the contacts 3|, and from there in parallel to the two gyroscopes 2| and 22, both of which have three-phase stators. For a more complete description of the follow-up system described, reference may be had to the prior patent of Wittkuhns and Watkins, l t-1,959,804, dated May 22, 1934, for Noncontacting follow-up systems.

The motor 5| is visible in Fig. -1 and is shown as connected by means of pinion 55, gear 55 and From the foregoing explanation it becomes evident that as soon as, due to an angular motion of the vehicle carrying the instrument, the gyroscopic element causes the shaft 1, and thereby the armatures 43 and 44, to turn in azimuth with respect to gear 31 and transformers 45 and 45, the motor 5| will start and run in a suitable direction to cause the follow-up transformers 45 and 45 to maintain their angular relationship with respect to the armatures 43 and 44. To do so, the motor turns the gear 31 and thereby also turns the bracket to which the free endof the horizontal hair springs 35. are connected, thereby preventing any change of the spring tension around the vertical shaft 1, which otherwise would create a torque around the vertical axis and thereby cause precession of the yro rotors in a vertical plane around pivots I8 and I9. Inasmuch as the cable 33 is quite flexible, considerable but limited angular displacement 'of the vention, the instrument cannot rotate through 360 in azimuth as finally the cable 39 would oppose such motion. However, anyone skilled in the art can easily connect the wires contained in cable, 39 to a set of slip rings carried on the bush-.

ing I2, from where the stationary brushes could conduct the current to the terminal block ll. It is understood, therefore, that this invention is not limited to gyroscopic devices of the type described, which only have a limited angular freedom.

Each of the gyroscopes 2I and 22 carries at its free end a pin 88 and 89, one of which is used as the point at which the caging mechanism can clamp the gyroscopie structure to a predetermined neutral position. As shown in Fig. 4, the caging mechanism itself consists of four arms I0, II, I2 and I3 adjustably mounted on gear sectors I4, I5, I6, and II in such a way that the relative position between the gear sector and the arm 10 can be experimentally determined and then secured by tightening of the screws 18.

and driving in dowel pins I8. All four gear sectors mesh with a central gear I9 which carries a pin 80 engaged by means of a slot with the arm 8|. This arm is secured to a gearrack 82' slidably mounted in two recesses under the bosses 83 and 84. The free ends of the gear rack are milled flat and have detents into which springs 85 and 86 can press loose pins 81 and 88 in such a way as to provide a definite rest for the rack 82 in its two end positions. The rack itself is actuated by a gear 89 secured to a shaft 90 and oper ated by a lever 9| from outside of the case (Fig Upon turning the lever 9I through a suitable angle, the rack 82 will be slid from one end position to the other end position, thereby forcing the pin 80 to follow this motion, which in turn causes the gear 19 to revolve through a predeterminedangle just sufilcient to close the four arms III, II, 12 and I3 around pin 89 in such a way as to securely hold this pin stationary. The length of the pin 89 and the opening between the four locking arms are so dimensioned that even at maximum angular displacement of the gyroscopic elements, the arms are still able to effect contact with pin 89.

Fig. 6 shows in detail one of the two identical gyroscopes 2| and 22. The end cap 92 may form part of the casting 20, as explained before. A

shaft 93 is held within the casing 2I by means of a pin 94 projecting into a slot in shaft 93,so that the shaft cannot rotate. Ball bearings 95 and 96 are provided to allow the rotor 91 to spin freely. This rotor has two side plates 98 and 99 which contain suitable recesses for the bearings 95 and 96. Rigidly fixed to the shaft 93 is a stator I00 consisting of a laminated structure .with insulating bushings IOI, through which a conductor I02passes to a cut out I93. The other end of the conductor is formed as a round head I04, and springs I05, mounted by means of insulated parts in the cap 92, serve the purpose of conducting current from the -..terminals I08 to the windings. The inner end of the conductor I92 is connected to one of the ends of the stator winding by means of globules I01 of a low melting solder alloy. The melting point of this'material is so chosen that it is somewhat above the normalopcrating temperature of the stator, so that in normal operation the alloy will not melt. If, however, due to failure of the bearings or other causes, the rotor 91 comes to a stop, the temperature of the stator windings will rapidly increase At least two of the contactors are provided with such springs, which by their initial tension make contact with buttons I I0, to which the ends of the windings inthe stator have been connected. The spring I08 is composed of thermostatic material which, as well known in the art, is composed of two dissimilar materials of different thermal expansion coeflicients. The spring is so arranged that at normal operating temperature of the windings, sufllcient contact pressure is provided for unimpeded passage of current. If, however, due to stalling of the rotor, the temperature in the windings increases, the thermostatic efiect of the spring I08 will finally open the contact, thereby interrupting the current supply to the windings. After the windings have cooled off sufiiciently, the decrease in temperature will cause the springs I08 to reestablish contact, whereupon the temperature in the windings will again start to increase. This device therefore enables the maintenance of a substantially I constant average temperature in the windings,

and thereby in the whole gyroscope, which is only slightly higher than the operating temperature and thereby'prevents the relatively large change in mechanical expansion which would result from allowing the windings to become completely deenergized and to cool off to room temperature. In other words, this device will prevent any appreciable variation in thermal expansion between developing around the vertical axis of the structure. It also will follow accurately any deviation from normal of the gyroscopic element caused by lateral turns of the craft carrying the instrument. It is therefore possibleto connect to the gear train 65, 68, 6'! another parallel gear train to drive a shaft extending from the instrument to a subsidiary instrument in which it is desired to obtain a motion proportional to the angular motion of the craft, and where considerable torque could be supplied by virtue of the driving torque of the power motor 6|.

As many changes could be made in the above construction and many apparently widely difierent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accomp n drawings shall be interpreted as illustrative and not in a limiting sense.

One of the advantages 0! the four-armed caging device described above is that it Provides a 5 and desire to secure by Letters Patent is:

1. In a gyroscopic direction indicating instrument, a support, ashait pivoted therein at the top and bottom for turning around the vertical axis, two equal and independent gyroscopes having horizontal spin axes, separate spinning means for each gyroscope, and means for symmetrically suspending said gyroscope on opposite sides of said shaitin neutral equilibrium for tiltin: around a horizontal axis normal to said spin axes with one gyroscope on each side 0! said vertical shait, whereby said neutral equilibrium is maintained regardless oi change of temperature.

2. In a gyrosoopic direction indicator, a support, a shaft pivoted therein for turning around,

a vertical axis, a pair of rigi ly connected substantially equal gyroscopes, each having a casing, a spinning motor and a rotor, and means to pivotally mountsaid gyroscopes in neutral equilibriinn on Opp site sides of said shalt symmetrical'to said vertical axis of said rotors, whereby said neutral equilibrium is maintained regardless of changes in temperature.

3. In a gyroscopic direction indicator, a support, a pair 0! substantially equal gyroscopes each having" a casing, a spinning motor and a rotor with a horizontal spin axis, a shait pivotally mounted in said casing for turning around a vertical axis, means for rigidly and coaxially' interconnecting said casings, and means for pivaround a horizontal axis normal to said spin axis,

whereby said neutral equilibrium is maintained 7 over wide ranges of temperature.

4. In a gyroscopic direction maintaining device, a gyroscopic sensitive element comprising two rigidly and coaxially connected gyro casings each containing a rotor electrically spun about a horizontal axis, means for symmetrically suspending said element in neutral equilibrium for turning around a vertical axis and tilting around a horizontal axis normal to said rotor. axis, a current's'upply forsaid gyroscopes, automatic means between said current supply and the winding of one gyroscope for breaking the circuit to said winding upon abnormal temperature rise therein, and a similar automatic circuit breaker between said current, supply and the winding of the other gyroscope whereby, on failure of one gyroscope, the other remains fully operative.

5. In an instrument as claimed in claim 4, said automatic means comprising a pair of normally contact making resilient strips 01' bi-metallic structure, said strips, by deforming, interrupting said supply as the temperatures rise above a predetermined value.

6. In an instrument as claimed in claim 4, said automatic means comprising a, globule of low melting soldering alloy normally connecting said supply to the windings of each of said gyroscopes,

whereby said supply to the aiIected gyroscope only is discohnectedby melting of said globule as the temperatures rise above a predetermined value, leaving the other gyroscope iully operative.

7. In a directional gyroscope, in combination with a rotor, an electric motor for spinning the same and a rotor casing, means pivotally supporting said casing for oscillation about a horizontal axis, a second means pivotally supporting the same for rotation about a vertical axis, a follow-up device about said vertical axis, light coil springs leading in current from said follow-up device to the gyro about the vertical axis, and separate light coil springs for leading in current about said horizontal axis, whereby all sliding contacts are avoided about both axes of support of the gyroscope.

' ORLAND E. ESVAL.

JOSEPH I 'REI'IAG. 

